Quantifying drought impacts on irrigation water requirements across major crops and growth stages in the Yellow River Basin

Study region The Yellow River Basin, China. Study focus Irrigation plays a critical role in sustaining agricultural development, particularly in water-scarce regions such as the Yellow River Basin (YRB). Yet, the response of irrigation water requirement (IWR) to drought events across different crop types and growth stages remained inadequately characterized. Here, we developed a daily-scale, multi-crop simulation framework that integrated the FAO Penman-Monteith method and the Standardized Precipitation Evapotranspiration Index (SPEI) to assess the spatiotemporal heterogeneity of IWR responses to drought events across four major crops (wheat, maize, rice, and soybeans) in the YRB during 1980–2018, which enabled systematic comparison of drought impacts across crop types and growth stages. New hydrological insights Drought significantly increased IWR for all crops, with basin-average increases of 27.70–31.36% during drought periods compared to non-drought periods. IWR increased consistently with drought severity, corroborated by significant linear correlations between SPEI and IWR anomaly, particularly in the Wei River Basin characterized by intensive irrigation and severe drought conditions. Specifically, rice exhibited the strongest sensitivity to drought across all growth stages, whereas the mid-season stage was identified as the most critical period for drought-induced IWR amplification for most crops. These findings moved beyond aggregate drought-impact assessments to provide an explicit understanding of irrigation sensitivity to drought, offering a scientific basis for targeted water allocation and drought adaptation strategies in water-stressed regions.